Imaging spectrometer reflectance data, mineral predominance map, and white mica wavelength position map, Nabesna Quadrangle, Alaska

Approximately 1,900 square kilometers of imagery were collected from July 14 to July 21, 2014 using a HyMap sensor (Cocks and others, 1998) mounted on a modified Piper Navajo aircraft. The survey area covered parts of the Wrangell and Nutzotin Mountains in the eastern Alaska Range near Nabesna, Alaska. The aircraft was flown at an altitude of approximately 5,050 meters (m) (3,480 m above the mean ground surface elevation of 1570 m) resulting in average ground spatial resolution of 6.7 m. HyMap measured reflected sunlight in 126 narrow channels that cover the wavelength region of 455 to 2,483 nanometers (nm). Data were delivered by the operators of the sensor (HyVista Corp., Australia) in units of radiance (Kokaly and others, 2017). Radiance data were converted to reflectance with procedures adapted from Kokaly and others (2013). The reflectance data are available upon request due to current size limitations. They are described and documented in this data release. Reflectance data from HyMap were processed using the Material Identification and Characterization Algorithm (MICA), a module of the USGS PRISM (Processing Routines in IDL for Spectroscopic Measurements) software (Kokaly, 2011), programmed in Interactive Data Language (IDL; Harris Geospatial Solutions, Broomfield, Colorado). MICA identifies the spectrally predominant mineral(s) in each pixel of imaging spectrometer data by comparing continuum-removed spectral features in the pixels reflectance spectrum to continuum-removed absorption features in reference spectra of minerals, vegetation, water, and other materials. For each pixel, the reference spectrum with the highest fit value identifies the predominant mineral class. A map of the wavelength position of the white mica 2,200 nm Al-OH absorption feature, elsewhere referred to more concisely as white mica, was also compiled. White mica wavelength position was computed for each pixel with spectrally predominant muscovite or illite. The computation was made using a function of the USGS PRISM software (Kokaly, 2011). The white mica wavelength values were output as a classification image, with classes in 1 nm increments. Each of these three datasets (reflectance, mineral predominance, and white mica wavelength position) are documented and described as part of this U.S. Geological Survey data release. REFERENCES Cocks, T., Jenssen, R., Stewart, A., Wilson, I., and Shields, T., 1998, The HyMap airborne hyperspectral sensor: The system, calibration and performance, in Schaepman, M., Schlapfer, and D., and Itten, K.I., eds., Proceedings of 1998 EARSeL Workshop on Imaging Spectroscopy, Zurich, Sweden, 68 October 1998; p. 3743. Kokaly, R.F., 2011, PRISM: Processing routines in IDL for spectroscopic measurements (installation manual and user's guide, version 1.0): U.S. Geological Survey Open-File Report 20111155, 432 p., available at https://pubs.usgs.gov/of/2011/1155/. Kokaly, R.F., King, T.V.V., and Hoefen, T.M., 2013, Surface mineral maps of Afghanistan derived from HyMap imaging spectrometer data, version 2: U.S. Geological Survey Data Series 787, 29 p., available at https://pubs.usgs.gov/ds/787/. Kokaly, R.F., Hoefen, T.M., King, T.V.V., and Johnson, M.R., 2017, Airborne imaging spectroscopy data collected for characterizing mineral resources near Nabesna, Alaska, 2014, U.S. Geological Survey Data Release, available at http://dx.doi.org/10.5066/F7DN435W.